Extra weight.

I am 19 and for about a year or so I have found that my face and chin have been accumalating alot of fat. I have IBS, when I've spoken to support groups they have said IBS doesn't cause you to gain weight. I have also gained weight round my stomach and breasts. I'm not obese but I have never been as big as I am now. I don't eat alot of fatty foods. It's really crippling my self esteem and I don't know what to do. Any ideas?